This proposal will continue the development of an efficient system to introduce exogenous molecules into eucaryotic cells by a lectin-mediated polyethylene glycol-induced liposome-cell fusion system. We will determine the parameters that are important to achieve high efficiency delivery of liposome-encapsulated molecules into cells while maintaining cell viability. The effect of the microinjection on cell metabolism including protein and nucleic acid synthesis, ATP pools, and growth rates will be studied. The location, function, dynamic interactions with cellular components, and fate of the microinjected molecules will be studied by radioisotopic and fluorescence techniques, including video intensification microscopy. The molecule that will be examined are fluorescent lipid analogs, fluorescent and radiolabeled proteins, including albumin and clatharin globin messenger RNA, and DNA. In order to optimize the biological liposome microinjection system, it is essential that the biophysical parameters that are operative for polyethylene glycol-induced fusion be better understood. We will determine the kinetics of polyethylene glycol-induced aggregation and fusion of liposomes using fluorescence and light scattering techniques, including carboxyfluorescein release and fluorescence of a terbium-dipicolinic acid complex. The effect of lipid composition, glycolipid lectin interactions, and concentrations of the various components of the system (polyethylene glycol, liposomes, lectins, molar ratio of glycolipid in the liposomes) on the aggregation and fusion between liposomes will be established. To corroborate the kinetic data, freeze fracture electron microscopy will be used to follow the morphology of the intermediates and final products of the polyethylene glycol-induced fusion between liposomes. The optimization of the technique as outlined in this proposal will provide a valuable tool for the study of cellular physiology, anatomy, and molecular biology in large members of living cells.